This case history of a central, site-wide district heat pump system illustrates how the operating- mode flexibility of the system’s two 850-ton (2992 kW) heat pumps enabled the system to remain cost-effective when major changes occurred in both utility rates and performance requirements. Both heat pumps can operate in three modes (heating, cooling, or simultaneous heating/ cooling), singly or in tandem, in the same mode or in different modes simultaneously.

Data are presented on load requirements, heat recovery, energy use, energy cost savings, and system payback for two very different operating configurations: one primarily heat recovery/ heating mode, the other primarily dual mode (simultaneous heating/cooling).

Units: Dual